KR20020031117A - Water Treatment Method for Screening Particles Containing Algae - Google Patents

Abstract

PURPOSE: A method of screening particles including algae, which can save the back washing cost for filter paper by preventing the clogging of the filter paper, is provided to apply without transforming of the previous system. CONSTITUTION: The screening system includes the follows; the sedimentation step includes the process of screening the particle including algae during overflowing the settling water; the screening is performed by mesh of which size of hole is 100¯150micrometer; the mesh has an inclination of 25¯35°from the overflowing part; the velocity of overflow is increased with 9.4¯14.4cm/s; a brush and a water supply equipment to block clogging by remove flocks on the mesh in the process;

Description

Water Treatment Method for Screening Particles Containing Algae

The present invention relates to a method for improving the water quality of filter paper influent by removing algae from the sedimentation basin of the water purification plant. More specifically, the present invention relates to a method of improving the water quality of filter paper inflow by filtering screen algae and flock particles present in the overflow water flowing into the filter paper from the sedimentation basin by installing a screen device in a weir at the upper part of the sedimentation basin.

Currently, water consumption is increasing rapidly due to economic growth and the improvement of living standards due to rapid urbanization. On the other hand, the discharge of various sewage, including living sewage, industrial waste and livestock waste, is increasing day by day. For this reason, the water shortage problem is a serious social problem in most middle and advanced countries including Korea. Therefore, in each country, many efforts are made to establish policies and prepare measures at the national level in order to solve eutrophication, phytoplankton outbreaks, and tastes in lakes and rivers, which are directly connected to the health of national life as well as natural ecosystem values. Is leaning.

The process of producing tap water involves first pouring water from the intake station in the water supply and then sinking the sand in the tap. Thereafter, various chemicals for water purification are added in the chemical input room, and water and chemicals are mixed well in the mixed paper. Thereafter, suspended solids and debris are entangled in the chemical in the flocculation paper, and then the tangled debris is precipitated in the sedimentation basin. The filter is then filtered more clean and chlorine is added to the chlorine feed chamber to kill any remaining bacteria. After that, completely treated water is stored and water is supplied to each household. There was a problem in that the filter paper is blocked because of particles such as algae flowing into the filter paper as it is not precipitated in the sedimentation basin during the process. Blocked filter paper has to be washed periodically, the cost was a big problem.

Increased phytoplankton biomass due to an increase in nitrogen (N) and phosphorus (P) nutrients due to water pollution, which leads to a decrease in transparency, a decrease in water treatment efficiency, and also causes problems such as filter paper clogging. do. This filter paper blockage phenomenon is particularly concentrated in the winter season and the spring season, and most of them are caused by diatoms. Stephanodiscus algae and Synedra algae are the main causes of filter blockage during the winter and spring seasons , and the Aulacoseira and Synedra algae in the fall. Algae are algae that cause filter paper obstruction. These algae did not process properly and went to the filter paper and acted as a major cause of filter blockage. For the normal functioning of the filter paper, it is necessary to periodically wash the blocked filter paper, such a backwashing has a costly problem.

The present invention is to solve the above problems, an object of the present invention, a method that can significantly reduce the backwashing cost of the filter paper by preventing the blockage of the filter paper can be easily applied without modification of the existing facility water treatment To provide a way.

1 is a perspective view showing a screen device equipped with a mesh used in the water treatment method according to the present invention.

Figure 2 is a perspective view showing the form of the screen device used in the water treatment method according to the present invention installed in the overflow portion of the sedimentation basin.

3 is a plan view showing the flow of the sedimentation index flows from the sedimentation basin to the filter paper.

* Description of the main parts of the drawings *

1 screen device 2 support plate

3: mesh frame 4: mesh

In order to achieve the above object, the water treatment method according to the present invention, in the water treatment process comprising a mixing step, a flocculation step, a precipitation step and a filtration step, the precipitation step, the sedimentation index flows into the filter paper while the algae It characterized by including the process of screening the particles containing.

In the above water treatment method, the screening is performed using a mesh made of holes larger than 100 µm and 200 µm or less.

In the water treatment method described above, the hole of the mesh is larger than 100 µm and smaller than 150 µm.

In the above water treatment method, the mesh is characterized in that it is installed obliquely at an angle of 25 to 35 ° from the overflow portion in which the sedimentation index flows. In particular, it is most preferable to be installed obliquely at an angle of 30 degrees.

In the above water treatment method, the overflow rate of the sedimentation index is increased.

In the water treatment method described above, the monthly flow rate of the settling index is 9.4 to 14.1 cm / s.

In the above water treatment method, the precipitation step, characterized in that to prevent the clogging of the mesh by continuously removing the floc attached to the mesh in the screening process.

In the above water treatment method, the floc is removed by a brush.

In the above water treatment method, the floc is removed by supplying water to the mesh.

Hereinafter, the water treatment method according to the present invention will be described in more detail.

In the water treatment method according to the present invention, water is freely passed through the supernatant of the sedimentation basin during the flow of the treated water from the sedimentation basin to the filter, and in consideration of particles such as algae and the cell size of the algae causing the blockage of the filter. Is to filter. The coarse filtration method according to the present invention can be easily applied since the biological activity is almost deteriorated due to the effect of chlorine treatment, flocculation chemical contact, etc. in the impregnation well-aggregation process, which is a preliminary step of the water treatment process. 3 is a plan view showing the flow of the sedimentation index flows from the sedimentation basin to the filter paper. When agglomerates settle in the sedimentation basin and clear water rises, the water flows out of the overflow and flows toward the filter. However, in order to solve the problem that the particles including algae do not settle and flow directly toward the filter paper beyond the overflow portion, it is essential to provide the screen device 1 of FIG. to be. The screen device 1 is preferably installed obliquely at an angle of 30 degrees from the overflow portion. That is, when the screen device is inclinedly fixed to the final weir of the sedimentation basin, the particles to be attached are combined with the outflow water flow rate and the cumulative weight of the particles to be adhered, thereby causing the particles to slide downward. Finally, the principle of natural sedimentation under the sedimentation basin is applied. In order to achieve the object of the present invention, the mesh should be 25 to 35 ° from the overflow. The reason is that when the angle of the mesh with the overflow portion is less than 25 °, the mesh's adhesion rate increases more than the sedimentation rate, which causes premature blockage of the mesh. Also, if the angle of the mesh with the overflow portion is greater than 35 °, the screen device according to the present invention starts to fully submerge under water, and water flows over the top of the screen device. 1 is a perspective view of a screen device 1 used in the present invention. The screen device 1 is composed of a mesh 4 for filtering out bodies, a mesh frame 3 for supporting the mesh 4, and a support plate 2 for supporting the mesh frame 3 from both sides. have.

Hereinafter, the present invention will be described in more detail with reference to one embodiment of the method according to the present invention, which is only for the purpose of illustrating the present invention and the scope of the present invention is not limited thereto.

Example

Comparative Example

The present inventors first investigated and analyzed the data necessary to grasp the actual condition of the conventional general water purification plant for the purpose of preparing for the effect of the algae and particles removal method of the water purification plant according to the present invention.

1. Survey on the distribution of algae in water purification plants nationwide

The present inventors analyzed the algae contained in raw water and sediment overflow water at 29 major water purification plants in Korea in November 2001 to find out the type and distribution of algae in the raw water and sediment overflow water of the water purification plant. As a result, 88 species of 48 genera of freshwater algae were observed. Among them, diatoms were 16 genera and 27 species (30.7%), cyanobacteria were 7 genera and 13 species (14.8%), green algae were 17 genera and 39 species (44.3%), whiskers were two genus 2 species (2.3%), yellow One species of flagella algae, one genus (1.1%), two species of euglena algae (3.4%) and three species of silver algae, three species (3.4%), diatoms, cyanobacteria and green algae accounted for about 90%. In other words, the algae in raw water and sediment overflowed in the water purification plant were in the order of green algae, diatoms, algae, euglena algae, silver and algae, and yellow algae.

According to the main composition of each taxa observed in the water treatment plant, diatoms were 1 species of Achnanthes , 1 species of Asterionella , 7 species of Aulacoseira , 4 species of Cyclotella , and cyme Cymbella 1 species, Diatoma 1 species, Fragilaria 1 species, Gomphonema 1 species, Gyrosigma 1 species, Melosira 1 species, Butterfly 2 Navicula , 1 Nitzschia , 1 Pinnularia , 1 Stephanodiscus , 2 Synedra and 1 Tabellaria , Cyanobacteria Anabaena 3 species, Aphanizomenon 2 species, Botryococcus 1 species, Merismopedium 1 species, Microcystis 2 species, Oscillatoria ( Oscillatoria ) 3 species and Phormidium 1 species, green algae are actinastrum ( Ac tinastrum ) 1 species, Ankistrodesmus 3 species, Chlamydomonas 1 species, Closterium 2 species, Coelastrum 2 species, Cosmarium ) 2 species, Crucigenia 1 species, Dictyosphaerium 1 species, Golenkinia 1 species, Gonium 1 species, Koliella 2 species, Micral Tiny Titanium (Micractinium) 1 species, pediah Sturm (Pediastrum) 5 species, ssene des mousse (Scenedesmus) 13 species, Selena Sturm (Selenastrum) 1 species, star Wu last room (Staurastrum) 1 species and hardware Stella (Westella) 1 species, dinoflagellates is a ssera tium (Ceratium) 1 species, ferry D nium (Peridinium) 1 species, yellow flagellum algae di knob ryon (Dinobryon) 1 species, euglena algae euglena (euglena) 2 species, Tra Kell One species of Trachelomonas , the flatworms are Chroomonas , Rhodomonas and Cryptomonas. ) Was included one each.

In addition, diatoms and cyanobacteria were predominant in the attached algae collected from scum and concrete wall substrate. The algae in the water treatment plant were particularly densely packed in the filamentous cyanobacteria, and the diatoms varied depending on the season. However, the typical flotation and adhesiveness were mixed, and the two characteristics of agglomeration and autogenous effects by chemicals could be considered.

Attached algae were 13 genera and 25 species, and southern algae were 4 genera and 5 species. The taxa are diatoms of 2 species Achnanthes , 1 species of Asterionella , 5 species of Aulacoseira , 5 species of Cyclotella , 1 species of Cymbella , and Dia. 1 Diatoma , 1 Diploneis , 1 Fragilaria , 1 Gyrosigma , 1 Navicula , 3 Nitzschia ), cine drive (Synedra) 2 species, other Bellaria (Tabellaria) 1 were paper, at least blue-green algae are Lying vias (Lyngbya), no stock (Nostoc) 1 species Oscillator thoria (Oscillatoria) 2 species, formate Medium ( Phormidium ) was one species. Excessive dense turquoise filamentous cyanobacteria on the inside and outside of scum in the sedimentation basin was mostly unseen in raw water, and it can be seen as a taxon that grows in the water purification plant. Along with the floating algae, it will be a significant contributor to the blockage of the filter paper.

2. Investigation of water quality at each stage of water treatment plant

The water quality of Suji and Cheongju water purification plants was analyzed by pH, electrical conductivity, turbidity, TDS, fluorescence measurement, chlorophyll a concentration, and inorganic nutrients in water. In other words, the water quality of raw water, mixed index, flocculation index, sedimentation index, filtered water and purified water was investigated. As a result, the water quality for the resin water purification plant is shown in Table 1 below, and the water quality for the Cheongju water purification plant is shown in Table 2 below.

As shown in the tables, turbidity was reduced by 79.4% in the resin water purification plant and 86.3% in the Cheongju water purification plant in the section from the raw water to the sedimentation basin. On the other hand, the fluorescence value decreased by 70.9% in the resin water purification plant and 81.7% in the Cheongju water purification plant. However, in the case of the resin water purification plant, turbidity tended to increase temporarily (2.57 → 4.31) immediately after the contact with chlorine, which is presumed to be caused by the concentration of algae and the destruction of the tank after chlorine contact. It can also be seen that the turbidity of the sedimentation index is significantly reduced in the filtered water. In other words, it indicates that the suspended solids in the sedimentation index is filtered through the filter paper. Thus, it can be inferred that the filter paper will occlude due to the attachment of the floats.

3. Determination of Algae Cell Counts by Water Treatment at Water Treatment Plants

(1) Preparation of Sample

In order to measure the change in algal distribution (cell number) according to the water treatment stage of a water purification plant, the inventors sampled samples from watering wells, mixed papers, flocculated papers, sedimentation papers, filter papers and water purification plants in June and November Got it. Samples for freshwater observation were mainly focused on quantitative analysis, and attached algae were focused on qualitative analysis. Samples for quantitative analysis were fixed with Lugol solution immediately after harvesting from each process of the water purification plant, and transported to the laboratory in an ice box. The attached algae were investigated in the sedimentation basin, and mainly the samples attached to the floating scum and the wall substrate within 1m of the sedimentation basin were collected. In particular, cyanobacteria and adherent algae were first observed as unfixed samples, and the fixed samples were sufficiently settled in the laboratory for 1 week or more, and then the supernatant was removed, concentrated 10 times to 20 times, and recrystallized as 1% formalin. At this time, the sample was wrapped in aluminum foil to prevent photooxidation.

(2) measuring the number of cells in algae

For identification of diatoms, 10 ml of the concentrated sample is mixed with an equivalent amount (1: 1) of nitric acid (HNO ₃ ) and then boiled, followed by acid treatment by adding a small amount of potassium dichromate (K ₂ Cr ₂ O ₇ ). It was. After acid treatment, the treatment reagent was washed several times with distilled water using a centrifugal separator, and a permanent specimen was made of Pleurax encapsulant, which was identified by microscopic examination under an optical microscope. For identification of species, observation was carried out at high magnification of × 400 or × 1000 times. A portion of the concentrated sample was evenly distributed in a 1 ml Sedgwick-Rafter chamber, and the number of species cells was counted while being examined under an optical microscope (× 200 times). The results are shown in the table below. Table 3 below is data for the resin water purification plant, and Table 4 below is data for the Cheongju water purification plant.

Taxonomy＼Sample Station R1 R2 M C S F T Basilario Picheae Bacillariophyceae ) Asterionella formosa Aulacoseira ambigua Aulacoseira ambigua f. spiral Auracoseira granulata Aulacoseira granulata var. Standing Bartica (Aulacoseira subartica) as angustissima aura kose a cycle L'Hotel La Atocha Moose (Cyclotella atomus) cycle Iberotel La menegini Ana (Cyclotella meneghiniana) cycle Iberotel La Stelliga Gera (Cyclotella stelligera) infrastructure Zilla Leah Black tonen system (Fragilaria crotonensis) Guy Gyrosigma spencerii Melosira varians Stephanodiscus hantzschii f. tenuis synedra acus 232, 3, 22,222, rr 24 3r22r2r2 r2, 33, 32r, rr 22233, 32r, r2r2 2 ... ··············· ··············· Cyanopicea Cyanophyceae ) Tesse (Gloeothece sp.) Oscillator Astoria (Oscillatoria sp.) In the flow ·· 3 ·2 2r ·2 ·· ·· Chloropicea ( Chlorophyceae ) Coelastrum reticulatum Coelastrum sphaericum Peelistrum Pediastrum boryanum Pediastrum duplex var. gracillimum Scenedesmus bicaudatus Scenedesmus longispina Scenedesmus quadricauda var. parvus ······· 3 ... 2 r 3,322 322 ... 2 ······· ······· ·······

(R1: impregnated crystal, R2: raw water immediately after chlorination, M: mixed paper, C: flocculated paper, S: settled paper, F: filter paper, T: purified paper, r: rare, 1: <10, 2: <100, 3: <1,000, 4: <10,000, 5:> 10,000 cells / ml)

Taxonomy＼Sampling Station R M C S F T Basilario Picheae Bacillariophyceae ) Asterionella formosa Aulacoseira ambigua Aulacoseira ambigua f. spiral Auracoseira granulata Aulacoseira granulata var. angustissima Aulacoseira italica Cyclotella meneghiniana Fragilaria crotonensis Gyrosigma spencerii Synedra acus 1323332rr1 13r3432rr2 2323432222 22 ... 2 ·········· ·········· Cyanophyceae Gloeothece sp. Oscillatoria proteus Oscillatoria sp. 2r R ··· ··· ··· ··· Chloropicea ( Chlorophyceae ) Scenedesmus ellipsoideus · r · · · ·

(R1: impingement well, M: mixed paper, C: flocculated paper, S: settled paper, F: filter paper, T: water purification paper, r: rare, 1: <10, 2: <100, 3: <1,000, 4: <10,000 , 5:> 10,000 cells / ml).

As shown in the table, it was found that a significant amount of algae is present in the sedimentation index (S) while no algae are present in the filter index (F). Therefore, it was easy to see that algae was caught while passing through the filter paper, and that the filtered algae would remain on the filter paper and eventually lead to blockage of the filter paper.

The resin water purification plant was found to be dominated by Aulacoseira , a diatom, and Oscillatoria , a cyanobacteria. As a result of quantifying the number of algae cells at each stage of the resin water purification plant, raw water was 560 cells / ml before chlorine contact, 2,618 cells / ml raw water after chlorine contact, 1,369 cells / ml miscibility index, and 779 cells / ml flocculation index. The index was 101 cells / ml. From this data, the algae content of the sedimentation index in the raw water before chlorine contact was 18.0%, and the water treatment efficiency was 82.0%. On the other hand, in case of Cheongju water purification plant, Aulacoseira , a diatom, was found to be the dominant point. The number of algae cells in the raw water of Cheongju water purification plant was 1,855 cells / ml, the mixing index was 2,570 cells / ml, the aggregation index was 2,787 cells / ml, the precipitation index was 115 cells / ml, and the precipitation index for raw water was 6.2%. Therefore, the water treatment efficiency was 93.8%. As a result, the effect of algae on filter paper can be seen in the range of 6.2 to 18.0%. Therefore, it can be seen that the algae removal rate (82.0%, 93.8%) is proportional to the turbidity reduction rate (70.9%, 81.7%). In other words, turbidity reflects a correlation with the effects of algae.

<Example>

<Examples 1 to 5: Evaluation of Turbidity and Algae Removal Efficiency by the Method of the Present Invention>

After mounting the screen device 1 having the support plate 2, the mesh frame 3 and the mesh 4 according to the method according to the present invention in the upstream part of the sedimentation basin. Twice a month, the removal efficiency of the sediment overflow algae was evaluated in the resin and water purification plants. As described above, since turbidity and algae are correlated, first of all, the turbidity of the sedimentation basin water before and after the screening device was measured and compared. In addition, the efficiency of removing algae by the screening device was calculated by measuring the algae cell number before passing through the screening device and the algae cell number after passing. The material of the mesh 4 was made of silk (Switzerland, Switzerland) which is widely used for the production of plankton net. The size of the screen device 1 was 100 cm × 18 cm, and the size of the mesh holes was 80 μm (Example 1), 100 μm (Example 2), 125 μm (Example 3), 150 μm (Example 4), respectively. And five kinds of meshes of 200 탆 (Example 5) were used. As shown in Fig. 1, each screen device 1 covered with each mesh used a mesh frame 3 in which both ends were obliquely fixed at an angle of 60 ° from the bottom by a support plate 2. . This screen device 1 was installed as it is in the sedimentation basin overflow section. That is, the mesh frame 3 is installed at an angle of 60 degrees from the surface of the water and at an angle of 30 degrees from the settling basin overflow portion. After installation as described above for 20 to 30 minutes, turbidity and algal cell number were measured. Thereafter, the particulate matter attached to the screen device 1 was collected by scraping with a soft brush and used for various analysis.

(1) Turbidity Removal Efficiency

The turbidity removal efficiency of the resin water purification plant is shown in Table 5, and the turbidity removal efficiency of the Cheongju water purification plant is shown in Table 6 below.

Size of mesh hole of screen device (㎛) Turbidity (NTU) Before the mesh passes After the mesh passed Turbidity removal rate (%) 80 0.44 0.34 22.0 0.34 0.33 0.46 0.29 100 0.35 0.30 37.0 0.40 0.28 0.63 0.28 125 0.32 0.28 76.6 0.58 0.30 2.81 0.28 150 0.70 0.30 40.4 0.40 0.25 0.32 0.30 200 0.55 0.27 37.2 0.35 0.27 0.40 0.27

Size of mesh hole of screen device (㎛) Turbidity (NTU) Before the mesh passes After the mesh passed Turbidity removal rate (%) 80 1.41 0.57 44.0 0.85 0.55 0.75 0.56 100 0.88 0.56 49.6 0.76 0.57 1.82 0.62 125 1.33 0.61 45.9 0.82 0.58 1.19 0.61 150 2.13 0.65 65.2 0.95 0.58 2.35 0.65 200 0.92 0.63 70.2 4.30 0.64 1.31 0.67

As shown in the table, the tendency of turbidity was irregular depending on the size of the holes of the mesh 4 of the screen device 1, but the turbidity removal effect was 22.0 to 76.6% in the resin water purification plant, and 44.0 to 70.2 in the Cheongju water purification plant. It was%.

(2) algae removal efficiency

The resin water purification plant is shown in Table 7 below, and the Cheongju water purification plant is shown in Table 8 below.

Taxonomy＼Sampling Station 80 100 125 150 200 B A B A B A B A B A Basilario Picheae Bacillariophyceae ) Asterionella linearis Asterionella formosa Aulacoseira granulata var. angustissima Cyclotella meneghiniana Navicula sp. Navicula sp. Stephanodiscus hantzschii f. tenuis 3 ······· ··2···· ······· 2 ... 2 ······· 2······ ······One ····2·· ·····One· Cynopicea ( Cyanophyceae ) Chroococcus mimutus Microcystis aeruginosa Oscillatoria sp. ··· ··· ·2· ··· ··2 ··· ··· ··· 2r 112 Chloropicea ( Chlorophyceae ) Coelastrum reticulatum Scenedesmus acutus var. acutus Scenedesmus longispina Scenedesmus quadricauda var. parvus ·2·· ···· ···· ···· 22 ···· 2··· ···· ···· ····

(80 μm, 100 μm, 125 μm, 150 μm, and 200 μm screen application, B: before passing the screen, A: after passing the screen, r: rare, 1: <10, 2: <100, 3: <1,000, 4: 〈10,000, 5:〉 10,000 cells / ml)

Taxonomy＼Sampling Station 80 100 125 150 200 B A B A B A B A B A Basilario Picheae Bacillariophyceae ) Asterionella ambigus Asterionella granulata Aulacoseira granulata var. angustissima Aulacoseira italica Cyclotella meneghiniana Fragilaria crotonensis Gyrosigma spencerii Navicula sp. Synedra acus 332 ········· 3121 ········· 2r3 ... 1 R ... r332 ········· 333 ... 2 11 ... Cyanopicea Cyanophyceae ) Oscillatoria sp. · · · · · · 3 · · ·

(80 μm, 100 μm, 125 μm, 150 μm, and 200 μm screen application, B: before passing the screen, A: after passing the screen, r: rare, 1: <10, 2: <100, 3: <1,000, 4: 〈10,000, 5:〉 10,000 cells / ml)

As shown in the table above, the removal efficiency of algae was 72.4 to 100%. In Example 1 (80 μm) and Example 2 (100 μm), the effect of removing algae was excellent, but the passage force through the screen device 1 decreased as time passed. In addition, Example 4 (150 μm) and Example 5 (200 μm) can solve the above-mentioned disadvantages, but the algae removal efficiency has dropped slightly to 72.4 to 98.6%. In the case of Example 3 (125 μm), while the algae removal efficiency was high, there was no tendency to decrease the water flow force passing through the screen device 1. Therefore, it can be seen that the size of the mesh hole is 125 µm (Example 3) having the highest algae removal efficiency. This size is effective in removing the diatom Synedra. Taken together, the size of the mesh holes should be at least 100 μm to prevent a reduction in the water flow through the screen device, and less than 150 μm to maintain high algal removal efficiency.

<Example 6 and Example 7: Full-scale Application Test>

In the full-scale test (second field test), the size of the screen device 1 is 250 cm x 18 cm x 2, and the size of the mesh hole 4 is 125 µm (Example 6) and 200 µm (Example 7), respectively. The screen device 1 was used. The full-scale test (second field test) focused on solving the head loss that may occur at the front end of the sedimentation basin due to the blockage of the applied screen device by supplementing the first test and suggesting an alternative. . As a result, turbidity was 96.9% in Example 6 (125 μm) and 94.9% in Example 7 (200 μm), which was slightly more effective in Example 6 (125 μm) but was not a big difference. The results for the removal of algae are shown in the table below.

Taxonomy＼Sampling Station S 125 200 Basilario Picheae Bacillariophyceae ) Asterionella ambigua Asterionella ambigua morphotyp. spiralis Aulacoseira granulata Aulacoseira granulata var. angustissima Aulacoseira granulata var. angustissima morphotyp. curvata Asterionella italica Asterionella subartica Cyclotella meneghiniana Cyclotella pseudostelligera Cycella ella Stella gera ) Cymbella sp . Gyrosigma spencerii Melosira varians Navicula sp. Pinnularia sp. Synedra acus 3233222213 ... r11 1 · 1r ··········· ·········One······ Cyanopicea Cyanophyceae ) Anabaena affinis Microcystis aeruginosa Microcystis ichthyoblabe Phormidium sp. 43 · 5 22 ... 23 ... Chloropicea ( Chlorophyceae ) Closterium sp. Staurastrum sp. ·One ·· ·· Euglenofikea ( Euglenophyceae ) Euglena sp. · · · Cryptopea Kea ( Cryptophyceae ) Chroomonas sp. Cryptomonas sp. ·· ·· ··

(S: the final overflow of the clarifier before passing the screen, 125: 125 μm, screen application, 200: 200 μm screen application, r: rare, 1: 〈10, 2: 〈100, 3: 〈1,000, 4: 〈10,000, 5 :> 10,000 cells / ml)

As shown in the table, the algae removal rate of Example 6 (125 μm) was 99.6%, and the algae removal rate of Example 7 (200 μm) was 99.1%. Therefore, when combined with the experiments for Examples 1 to 5, it can be determined that the preferred size of the mesh 4 holes in the method according to the present invention is 100 µm to 200 µm. It was confirmed that the algae filtered through the screen device 1 according to the present invention are also filtered by algae other than the original diatoms, Synedra acus , such as adherent algae and aggregates (flocs) by scum. In addition, it was confirmed that it can remove not only algae but also abiotic particles. The body which passed through the screen device 1 without being filtered out was a very small species, and the diatoms Aulacoseira subartica , Cyclotella pseudostelligera , and Cyclotelella Stelligera . ( Cyclotella stelligera ), cyanobacteria Anabaena affinis , and Microcystis aeruginosa . However, the effect of the filter paper blockage by the amount of the algae passing through the screen device is very small, compared to the initial amount flowing through the settling basin portion and flowing into the filter paper without applying the screen method according to the present invention. I think it is small.

However, the inventors of the present invention can further improve the effect of the present invention if particles such as algae are attached to the screen device 1 to prevent clogging of the screen and prevent head loss that may occur at the front end of the upstream portion of the settling basin. Found. This is described in Examples 8 to 10 below.

Example 8

In Example 6 and Example 7, the experiment was carried out under the same conditions as in Example 6 and Example 7, except that the monthly flow rate was increased by 2-3 times. The conventional overflow flow rate is 4.7 cm / s and very slow enough to be affected by the wind. In Example 8, the overflow rate was set to 9.4 to 14.1 cm / s. As a result, the mesh of the screen device 1 was hardly blocked.

While the sedimentation index flows through the overflow portion, a problem may occur in that the mesh of the screen device 1 is blocked due to the stickiness of the floc, thereby causing head loss in the sedimentation pond. This problem can be solved by increasing the overflow rate as in the eighth embodiment, thereby further improving the effect of the present invention.

Example 9

The screen device 1 was carried out in the same manner as in Example 6 and Example 7, except that a brush was further provided. The brush serves to scrape off the particles attached to the mesh 4 during the overflow of the sedimentation index from the sedimentation basin. Therefore, it was possible to further improve the effect of the present invention by preventing the blockage of the mesh.

Example 10

It carried out similarly to Example 6 and Example 7 except having further equipped with the means which inject | pours water from the rear end of the screen apparatus 1. The problem of blockage of the mesh can be solved by preventing the particles from adhering to the mesh 4 by spraying water at the rear end of the screen device 1. Therefore, the effect of this invention was further improved.

By using the water treatment method according to the present invention, not only most algae and agglomerates (flocs), including adherent algae by scum, can be removed at the stage where the sedimentation index flows through the sedimentation basin overflow portion during the flow from the sedimentation basin to the filter paper. Even non-biological particles can be removed. Thus, by preventing particles from flowing out of the sedimentation basin causing blockage of the filter, not only can the purified water quality be improved, but also the backwashing cost of the filter can be significantly reduced. In addition, the water treatment method according to the present invention has the advantage that it can be easily applied without modification of the existing facility.

Claims (9)

In the water treatment process comprising a chemical mixing step, a flocculation step, a precipitation step and a filtration step, The sedimentation step, the sedimentation index water treatment method comprising the step of screening the particles including algae during the overflow into the filter paper. The water treatment method according to claim 1, wherein the screening is performed using a mesh made of holes larger than 100 µm and smaller than 200 µm. The water treatment method according to claim 2, wherein the size of the mesh hole is larger than 100 µm and smaller than 150 µm. The water treatment method according to claim 2, wherein the mesh is obliquely installed at an angle of 25 to 35 degrees from the overflow portion through which the sedimentation index flows. The water treatment method according to claim 1, wherein the monthly flow rate of the sedimentation index is increased. The water treatment method according to claim 5, wherein the monthly flow rate of the settling index is 9.4 to 14.1 cm / s. The water treatment method of claim 2, wherein the precipitation step continuously removes the floc attached to the mesh during the screening process to prevent blockage of the mesh. 8. The method of claim 7, wherein said floc is removed by a brush. 8. The method of claim 7, wherein the floc is removed by supplying water to the mesh.